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461.
A laboratory simulation of rock breakdown due to freeze-thaw in a maritime Antarctic environment 总被引:1,自引:0,他引:1
Kevin Hall 《地球表面变化过程与地形》1988,13(4):369-382
Results of freeze-thaw simulations on three large blocks of quartz-micaschist are presented. Three types of water to ice phase change were identified from temperature and ultrasonic measurements. It is suggested that the type of phase change results from a particular combination of rock moisture content, solute concentration, freeze amplitude, and rate of fall of temperature. The temperature at which ice thawed inside the rock (?0.7 to ?1.9°C) was also found, and this indicates the possibility of freeze-thaw effects without positive temperatures. Approximately 80 per cent of the water that will freeze under natural conditions, in the Maritime Antarctic environment under study, appears to have done so by ?6°. 相似文献
462.
Freshwater mills historically were found throughout England serving a wide variety of uses. The decline in the need for water power over the last 100 years saw a reduction in the number of operational mills. Despite this decline, the associated river structures were rarely removed and many of these have exceeded their design life and have failed or are now starting to fail, with important geomorphological implications for the river. This paper investigates the geomorphological impacts of mills and their structures on English rivers, and considers their legacy for the contemporary management of these systems. 相似文献
463.
464.
Kevin Hamilton 《大气与海洋》2013,51(2):188-192
Abstract The initial development of the westerly acceleration phase of the tropical quasi‐biennial oscillation in late 1979 was examined using FGGE analyses at the 20‐ and 10‐mb levels. The analysed winds were found to undergo strong equatorially‐centred westerly accelerations. These accelerations are narrower in meridional extent than those expected to result from the interaction of the Wallace‐Kousky Kelvin wave with the mean flow. 相似文献
465.
The mitre squid(U roteuthis chinensis) and the swordtip squid( U. edulis) are Indo-Pacific cephalopod species that are abundant in the western Pacific Ocean. They are currently exploited in the East and South China Seas and make up a significant portion of the Chinese neritic squid catch. Beaks, the feeding organs of squid, are important for individual size and biomass estimation because of their high resistance to degradation in predator stomachs and consistent dimensions. In this study, 104 U. chinensis and 143 U. edulis individuals were sampled from northern South China Sea with mantle length from 70 to 260 mm and 96 to 284 mm, respectively. The results indicated that morphological beak values were greater for U. edulis, compared to U. chinensis, for upper hood length(UHL), upper crest length(UCL), upper lateral wall length(ULWL), lower crest length(LCL), and lower lateral wall length(LLWL). According to principal component analysis, UHL/ML, UCL/ML, ULWL/ML, LCL/ML, LLWL/ML and LWL/ML could represent the characteristics of beaks for U. chinensis, while UHL/ML, UCL/ML, ULWL/ML, LHL/ML, LCL/ML and LLWL/ML could represent it for U. edulis. According to Akaike's information criterion(AIC) values, a power function was the most suitable model for U. chinensis, while a linear function was the most suitable model for U. edulis. The beak variable-mantle length ratio(beak variable/mantle length) declined with the increasing of mantle length and declined sharply at the early stage of growth in both beaks and species. The ratio changed quickly after achieving the mantle length of 140 mm for U. chinensis, while the ratio changed quickly after 170 mm for U. edulis. Beaks in both species experienced sharper changes through maturity stage I to II than other maturity stages. This study gives us basic beak morphology information for U. chinensis and U. edulis in the East and South China Seas. Geometric morphological methods combined with dietary analysis should be used in the future. 相似文献
466.
Michael K. WEISBERG Caroline SMITH Gretchen BENEDIX Christopher D. K. HERD Kevin RIGHTER Henning HAACK Akira YAMAGUCHI Hasnaa CHENNAOUI AOUDJEHANE Jeffrey N. GROSSMAN 《Meteoritics & planetary science》2010,45(3):449-493
Abstract– In this edition of The Meteoritical Bulletin, a total of 506 newly approved meteorite names with their relevant data are reported. These include 354 from northwest Africa, 31 from the Americas, 15 from Antarctica (Koreamet), 85 from Asia, 20 from Australia, and 1 from Europe. Among these meteorites are 2 falls, Grimsby (Canada) and Santa Lucia (2008) (Argentina). Also described are a CM with low degree of alteration, new ungrouped chondrites and achondrites, and 4 Martian meteorites. 相似文献
467.
The Mariner 9 ultraviolet spectrometer observed the brightness of a region on the south polar cap centered at approximately ?87°S, 10°W. Measurements taken at various incidence and emission angles (i and ?) show that the brightness increased with decreasing air mass, ≈(sec i + sec ?). The observed intensity consists primarily of a component reflected from the cap and twice-attenuated by the atmosphere and a component diffusely reflected from the atmosphere. The diffusely reflected component was determined from nearby observations of non-polar regions at the same incidence and emission angles and was substrated from the total intensity. Inversion of the intensity difference using a formula analogous to the Bouger-Langley law yielded the optical thickness of the atmosphere. The dust cloud over the polar cap was moderately thick between November 26 and December 2, 1971. At this time the optical thickness was near unity, and it decreased approximately linearly with time, reaching a value close to that of a Rayleigh atmosphere by mid-February. The optical thickness showed little dependence on the wavelength during the early orbital observations. As the dust storm cleared, the atmospheric optical thickness exhibited increasingly strong inverse wavelength dependence. Particles large compared with the wavelength dominated the Martian dust storm. These particles are estimated to have a mean radius of about 2 μm. 相似文献
468.
Kevin J. Coakley 《Mathematical Geology》1992,24(8):905-927
Steady-state laminar flow through single rock fractures is predicted in terms of spatial statistics computed from the arrangement of voids and contact areas within the fracture. Within the voids, aperture is assumed to be constant. One statistic measures how often pixels alternate from void to contact area in the rows parallel to the flow direction. Two others measure the dispersion of voids in the rows and columns of the pattern. Fractures with complexity typical of observed data are simulated. Flow through patterns with 80% voids is predicted in terms of a linear combination of the three statistics. Using an extended model involving one of the three statistics, flow through patterns with other void fractions is predicted.The author did this work at the Earth Sciences Division at Lawrence Berkeley Laboratory, Berkeley, California. It is part of a Ph.D. thesis which was submitted at Stanford University. 相似文献
469.
470.
We present and interpret observations of the preflare phase of the eruptive flare of 15 November, 1991 in NOAA AR 6919. New
flux emerged in this region, indicated by arch filaments in Hα and increasing vertical flux in vector magnetograms. With increasing
frequency before the eruption, transient dark Hα fibrils were observed that crossed Hα bright plage and the magnetic inversion
line to extend from the region of flux emergence to the filament, whose eruption was associated with the flare. These crossing
fibrils were dynamic, and were often associated with sites of propagating torsional motion. These sites propagated from the
region of flux emergence into the filament flux system. We interpret these morphological and dynamic features in terms of
relaxation after magnetic reconnection episodes which create longer field lines within the filament flux system, as envisioned
in the tether cutting model, and transfer twist to it, as well.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1005086108043 相似文献